The file format lacks the correct date value for each trackpoint, so it has to be computed starting from the
date given in the filename. To handle files without a parsable date in the
name, the command line option 'date' is provided.

Conversions from gopal into any other format are a bit lossy concerning the first field of each line wich looks like an useless time tick value
and is simply discarded while reading. If written, there will be a time_t value from the current (computed) timestamp.

Somewhere around Gopal 4.8 or 5.0, Electrobit added three more fields to the end of this format. They are, in order, date (which eliminates most of the silliness above), an unknown field, and a bearing. GPSBabel now reads the date and ignores the other two. We don't yet write these three fields for compatibility with earlier versions.

Filtering out invalid data points is handled by the options 'clean', 'minspeed' and 'maxspeed'.
For each datapoint the speed needed to come the from the last valid point is
calculated and compared with the limits.
Thus one cat easily discard unreliable points.

date option

Complete date-free tracks with given date (YYYYMMDD)..

This option is useful if you have tracks from Gopal that have been renamed.

maxspeed option

The maximum speed (km/h) traveling from waypoint to waypoint..

This is useful for removing wildly erroneous data from your recorded track.

minspeed option

The minimum speed (km/h) traveling from waypoint to waypoint. Set &gt;0 to remove duplicate waypoints.

If this is greater than zero, duplicate waypoints will be removed.

clean option

Cleanup common errors in trackdata.

Specifying the clean flag makes the Gopal reader pass
over the data and discard data that is probably incorrect such as the
longitude and latitude of "0".

If you happen to be a boater or pilot off the south short of Ghana,
you may disagree that coordinates of "0, 0" are bad.